Hearing impairment is the United State's number one disability. It has been estimated to compromise the quality of life and communication in more than 30 million Americans, and approximately 1 billion individuals worldwide. With the increase in longevity in life and the association of hearing impairment with aging, this disability is increasing in incidence and prevalence. In children, it severely affects education and future employment opportunities. In a working individual, it compromises the quality of life, job satisfaction, and productivity; and in the elderly, it leads to isolation and increased medical costs.
Sensorineural hearing loss is better known as nerve deafness. This is behind 95% of all hearing problems. It usually happens because the tiny, sound-transmitting structures deep within the ear wear down or get damaged. Sound enters the inner ear, but it doesn't get sent to the brain in the right way. Nerve deafness can be caused by loud noise, use of ear-damaging or ototoxic drugs, infections like measles and meningitis, an accident or trauma, or a birth or hereditary defect. Treatments for nerve deafness (e.g., hearing aids), allow for improved hearing and improved quality of life in some individuals.
The remaining 5% of hearing problems are due to conductive hearing loss. In these conditions, sound is not transferred from the outer to the inner ear. Conductive hearing loss can result from a punctured eardrum, severely impacted earwax (cerumen), head trauma, birth defects, or heredity.
For patients with profound deafness, cochlear implants may provide some sound and often prove quite helpful. Though they can't restore natural hearing, cochlear implants produce hearing sensations in the ear. While cochlear implants have provided a huge advance in the treatment of profound hearing impairment, patient performance remains highly variable, and even in the best cases, implant performance is far below that of the native, normal inner ear. Thus, methods of treating deafness and improving the outcome of profoundly deaf patients are needed.